Wireway systems including channel-shaped ducts having upstanding fingers constituting slotted side walls have been in general use for years because of their convenience in channeling, selectively routing and retaining the various wires of a wire bundle interconnecting the components of an electrical system. These ducts typically have a cover for retaining the wires in the duct after completion of the wiring. A problem encountered with the use of such ducts is that during the wiring or when the cover is removed to permit maintenance, individual wires may tend to fall out of the duct due to the resiliency of the wires. This problem is particularly acute when the duct is nearly filled with wires or when the duct is vertically mounted.
Because of these difficulties, plastic retaining fingers have been proposed for retaining previously installed wires in the duct until the wiring is completed and the cover mounted on the duct. These various retaining fingers attach to one wall of the duct and extend partially across the duct opening.
More particularly, one such retainer has a bifurcated base portion comprising resilient legs for engaging the wall and a finger portion extending from the base portion partially across the duct opening. When such a finger is attached to the sides of adjacent upstanding fingers forming a slot in the wall, the retaining finger tends to fall to the bottom of the slot where it interferes with the introduction of additional wires in the duct. This occurs because the force applied by the resilient legs slightly deflects the upstanding fingers in the longitudinal direction of the duct. To overcome this disadvantage, auxiliary closed slots for mounting the retaining fingers are required in the individual upstanding fingers. However, the closed slots typically do not extend near the top of the duct wall, thus precluding use of the retaining finger when the duct is nearly filled with wires. Furthermore, the resiliency of the legs diminishes with repeated usage or when the retaining finger is subjected to heat, causing the plastic to soften, as when the wireway system is mounted on a hot control panel. Such a wire retainer is shown in U.S. Pat. No. 3,705,949.
Another type of retainer was proposed which was disposed between two adjacent side wall fingers. This design did not use resilient legs to engage the fingers, rather a more rigid finger design was used. This design incorporated two small plane portions, separated by the thickness of the side wall fingers, which were ratcheted between two adjacent fingers then locked into a maximum vertical height position. This is the only height position which may be selected, and if the retainer is not locked into the maximum height position, it will fall to the bottom of the duct wall where it interferes with the introduction of additional wires into the duct. Another disadvantage is the extreme ratcheting and corresponding bending of the side wall fingers which is required, and consequently makes installation very difficult. Furthermore, since the planar portions are relatively small, when the retainer is bumped or jarred, it easily becomes displaced from a mounted position. The reason for this is that the bumping or jarring action often mimics the installation procedure, thus unistallation is common. The result is a wire retainer which is limited in use, difficult to install, and easy to displace unintentionally. Such a wire retainer is shown in U.S. Pat. No. 3,890,459.
A third type of wire retainer engages a single specially-made duct finger with resilient C-shaped legs and a groove or bump engaging locking mechanism. Each duct finger has a multitude of grooves or bumps disposed thereupon to permit segmented height adjustment of the wire retainer. A projection or dog is disposed upon the wire retainer which engages the groove or bump and secures the retainer into position. However, such an arrangement does not adequately permit a maximum height selection when used with a duct cover. Furthermore, the intricate design of the wire retainer makes it difficult and expensive to manufacture. The specially required duct is also more expensive to manufacture, but necessary in order to provide selective height adjustment. The result is a wire retainer which is complicated and expensive to manufacture and only provides complete performance with one specific certain type of wiring duct. Such a wire retainer is shown in U.S. Pat. No. 4,136,257.
One major disadvantage of all of the prior art designs is that each will only work with one certain type of duct, that which is specifically manufactured for it.
Therefore, in the design of wire retainers, a less expensive, easier to manufacture and more widely applicable design is desired and improvement in the art of wiring duct wire retention is needed.